This invention is directed to a current carrying hose assembly particularly for the use as a flexible hose for a vacuum cleaner, where electric current and fluid flow pass through the same flexible member.
One specific type of vacuum cleaner is referred to as the tank type which has a vacuum hose connected to a tank at one end and the other end may be, for example, coupled to a cleaning tool. This cleaning tool may have a rotatable brush and an electric motor therein for rotating the brush. The brush works and agitates the area being cleaned at the same time it is vacuumed so that loosened dirt material is picked up and drawn into the flexible hose and emptied into the vacuum cleaner tank.
In the usual embodiment an electric motor driven vacuum fan is placed in the tank and it is electrically connected to an electric supply by an electric input cord which supplies power to drive the vacuum fan. It is next necessary to provide electric current to the electric motor in the cleaning tool for rotation of the rotary brush. This is either by a separate pair of wires or by electrical wires helically wound integrally within the flexible hose.
In some embodiments, the electrical conductors within the hose themselves provide the very spring which makes the hose flexible so that it will bend in a desired shape without collapsing of the hose. In such a case, the wires may be stiffened by and insulated with a coating of polyvinyl chloride, for example.
In some prior art devices, two separate vinyl coated wires are helically wound in a two start helix so that each wire is helically spaced from the other wire.
A polyvinyl chloride cover is wrapped wround the spaced wires or may be extruded in the manner well known to those skilled in the art. The prior art tubes are normally in the form of two single insulated copper conductor wires for the helices and a thermoplastic film for the vacuum tube which forms the hose. End fittings are then molded to the hose so that the hose can then be fitted to other equipment, for example, to the tank of the vacuum cleaner on one end and to the rotating brush pickup head on the other.
In manufacture of these prior art flexible hoses, the process involves two parallel conductive wires wound simultaneously around the mandrel in two helices. The mandrel is then fed to a crosshead extruder where a film of thermoplastic is extruded over the wires to form the cover of the hose. Hoses with fixed end fittings can only be manufactured in the same length as the mandrels. The wiring harness is connected to the helical conductors with insulated connectors. The hose end and harness are then placed in a mold cavity and the end fittings are molded around the end of the hose, capturing and covering the two connectors. This, of course, provides the basic disadvantage that one cannot visually inspect the wiring connectors after the end fittings are molded. The connectors are not separated from each other before the end fittings are molded on so that short circuit problems do occur. Molded hose ends cannot be repaired in the field by qualified repairmen. This type of prior construction is represented by Holden, U.S. Pat. No. 3,928,715 and Pauler et al, U.S. Pat. No. 3,034,085.
The present invention overcomes the aforementioned disadvantages of the prior art and provides a new and improved current carrying hose assembly which can be made in any length desired and includes strain reliefs which are locked into the end fittings keeping the wire connectors secure, and mechanically and permanently separated from each other. The conductors, as provided in the present invention, are double insulated and can be inspected to insure good connection of conductors and wiring harnesses after end fittings have been assembled. The end fittings and hose assemblies can be repaired in the field at any time by qualified repairmen.